1. Field of the Invention
The present invention relates to a method for correcting symbol timing and the apparatus thereof, especially to a method for correcting the symbol timing of a receiver and the corresponding apparatus.
2. Description of the Prior Art
In the field of digital communication, the transmitter transmits signals carrying digital data to a receiver with a specific symbol timing T1. After receiving the signals, the receiver recovers the digital data by sampling the signals according to a specific symbol timing T2. If the symbol timing of the receiver T2 is the same as the symbol timing of the transmitter T1, and no phase delay between the two timings, the receiver will recover the digital data correctly. Oppositely, if the symbol timing T2 is different from the symbol timing T1, or having phase delay between the two timings, the receiver will not recover the digital data correctly. Accordingly, a critical mechanism is required to be set in the receiver for ensuring that the symbol timing T2 of the transmitter is synchronizing with the symbol timing T1 or that the timing reference of the receiver has a certain relation to the timing reference of the transmitter by signal processing.
Generally speaking, for synchronizing the symbol timing T2 of the receiver with the symbol timing T1 of the transmitter, the receiver calculates the sampled data by utilizing a timing recovery algorithm (TR algorithm) to obtain timing metrics, which are related to the difference of the timing references (i.e., the timing error) of the transmitter and the receiver, and are advantageously utilized to correct the symbol timing of the sampling circuit of the receiver. Once the symbol is corrected, the symbol timing T2 is synchronizing with the symbol timing T1 or there is a certain relation between these two timings. Please refer to the flowing journals for detailed description: K. H. Mueller and M. Muller, “Timing Recovery in Digital Synchronous Data Receivers,” IEEE Trans. Communications, vol. Com-24, pp. 516-531, May 1976, and F. Gardner, “A BPSK/QPSK Timing-Error Detector for Sampled Receivers, “IEEE Trans. Communications, vol. Com-34, pp. 423-429, May 1986.